1、 Introduction
Insulation technology refers to the use of electronic technology, computer technology, sensing technology, through the operation of high voltage electrical equipment to carry out signal acquisition, transmission, data processing, logical judgment, in order to power equipment in the running state, live test and real-time monitoring, diagnosis. The reliability of power system is directly related to people's daily life and production, the normal and safe operation of the high voltage electrical equipment is the basis of the normal and safe operation of the power system, and it is also the most important. With the development of economy and society, the power system is developing rapidly along with the pace of the times. At the same time, the insulation technology also arises at the historic moment. Next, based on the analysis of insulation technology, the application of insulation technology in high voltage electrical equipment is discussed.
2、The principle and function of insulation technology
(1) Monitoring objects and parameters
High voltage electrical equipment insulation technology is the use of high voltage electrical equipment working voltage monitoring insulation characteristic parameters in the process of high voltage electrical equipment operation. Therefore, it can accurately reflect the operation condition of the insulation of high voltage electrical equipment, and then make accurate judgement of the insulation condition. Insulation technology is monitored according to the different electrical equipment in the substation. The monitoring contents include capacitance, loss value, bus voltage, insulation resistance, unbalanced three-phase signal, leakage current and other parameters. With the continuous development of insulation technology, the electrical quantity of its monitoring is also increasing.
(2) The function of insulation monitoring
Insulation technology can measure the insulation characteristic parameters of live equipment in real time, and can also analyze and process data.
① Monitor the changes of resistive current and capacitive current during the operation of the arrester, and understand the internal insulation and valve aging.
② Monitoring the dielectric loss and leakage current of capacitive equipment such as coupling capacitor, CVT, casing, current transformer and other capacitive equipment, to understand its internal insulation aging, moisture and damage defects.
③ The monitoring impedance is stable and will not be affected by the electromagnetic interference of the substation. It is self guaranteed under the action of the system lightning and overvoltage, and no software damage and performance change occur.
④ Monitor the change of the flammable gas in the insulating oil, and know whether there are any defects such as discharge and overheating inside the equipment.
3、Related knowledge of insulation equipment
The analysis of insulation equipment can be from the following points:
(1) Lightning arrester
Now, the lightning arrester in the substation has no series gap, the high voltage electrical equipment will leak a part of the current through the valve plate to speed up the aging speed of the valve plate, and the main factor of the deterioration of the valve plate of the high voltage electrical equipment is aging and dampness. Monitoring the current leakage of high voltage electrical equipment can effectively observe the insulation of high voltage electrical equipment. The measurement current reflects the severe tide, the resistance current increases in the early age of aging, and the total current has no obvious change. When the high voltage electrical equipment is running normally, it is capacitive current through the arrester, and a small part is resistive current, which accounts for about one to 20%. The resistive component covers the leakage of internal and external surfaces of the porcelain bushing, leakage of valve plates and resistance components, and leakage of insulation support. Whenever the surge arrester is dampened, the valve piece is ageing, the insulation parts are damaged and the surface is fouled, the capacitive current does not change significantly, but the resistive current is increased. The main cause of the lightning arrester is increasing the resistance current and increasing the loss, resulting in thermal breakdown.
(2) Coupling capacitor, CVT, current transformer
Monitoring the positive tangent value of the dielectric loss angle of the coupling capacitor, CVT and current transformer is a highly sensitive item, and the insulation deterioration of the high voltage electrical equipment, the insulation dampness and the local defects can be found. The insulation dampness accounts for more than 80% of the equipment, because the structure of the equipment is the average pressure of the capacitance distribution, the high insulation coefficient, the insulation dampness will lead to the increase of dielectric loss and the breakdown.
The basic characteristics of insulation deterioration:
① The dielectric loss of insulation increases, and heat causes thermal breakdown. The dielectric loss angle can be used to monitor the change of dielectric loss.
② Insulation will occur in partial discharge and partial discharge. The large amount of partial discharge occurs under overvoltage, lightning and insulation damage. Dielectric loss can be calculated through measurement.
③ Insulation characteristics can vary with temperature.
The insulation temperature is determined by the size, type and condition of insulation. The temperature increases, and the sensitivity and temperature increase linearly with the relative design and grade. Therefore, the influence of ambient temperature, dielectric loss and load on the aging insulation value is obvious.
Monitoring of dielectric properties with capacitive insulation will detect developmental defects at an early stage. At the beginning of the development defect, the measurement of the positive tangent value and the increase rate of the dielectric loss is the same, with high sensitivity. In the later period of the development of the defect, the changes in the measurement current and capacitance are the same, and it is easier to monitor the development defects.
4、Application of high voltage electrical equipment to insulation technology
It is of great significance to adopt insulation technology in high voltage electrical equipment of industrial and mining enterprises. In order to ensure the safe and stable operation of electrical equipment and effectively prevent the equipment from being damaged, it is necessary to strictly protect the electrical equipment and power supply system. In addition, according to the actual situation, the electric equipment and power supply operation of the industrial and mining enterprises are fully mastered, so that the normal operation of the production activities of the industrial and mining enterprises can be effectively guaranteed, so that the production efficiency of the industrial and mining enterprises can be further improved. The insulation technology of high voltage electrical equipment is a comprehensive technology, which integrates computer, communication, high voltage and test. Digital signal transmission, sensor and state diagnosis are the core. The application of insulation technology in high voltage electrical equipment is a necessary means to realize condition based maintenance. The application of insulation technology helps to transition from regular maintenance to state maintenance. The use of insulation technology for state maintenance can be realized.
(1) Effectively prevent the disadvantages caused by periodic plan and maintenance, plan to arrange the maintenance, save the maintenance cost, make the operation equipment keep normal operation and create economic benefit.
(2) Reduce the blindness of the test and maintenance of high voltage electrical equipment, reduce the probability of failure in the process of overhaul of the high voltage electrical equipment, prolong the use period of the equipment, and make the maintenance of the equipment more scientific and reasonable.
(3) Greatly reduce switching operation and power failure time, improve the power system's economy, stability and safety.
(4) Continuously and correctly reflecting the insulation performance and troubleshooting of the voltage of the high voltage electrical equipment, monitoring the lack of insulation in the operation of the high voltage electrical equipment in time, preventing the occurrence of the sudden insulation, effectively improving the running of the high voltage electrical equipment, reducing the probability of the accident, and obviously reducing the sudden accident. So.
(5) The insulation technology can make up the preventive test, combine the insulation technology with the preventive test, arrange the pretest according to the result of insulation technology and improve the repair cycle. It is an effective measure to promote the state maintenance in an all-round way.
The state maintenance should master and know the insulation parameters of the charged condition of the high voltage electrical equipment, and the insulation technology is the way to obtain the insulation parameters of the charged condition of the high voltage electrical equipment. Under the condition of the operation of high voltage electrical equipment, the state parameters of the insulation are monitored, and the parameters are compared and analyzed, in order to decide whether to overhaul or not. For the supervision and management of high voltage electrical equipment, it is also required that the external insulation surface can not be polluted seriously; its porcelain sleeve, flange and composite coat can not appear crack, discharge burn and breakage. To ensure that the porcelain coat coated with RTV coating has a good hydrophobicity, the coating must not appear defect and crack. At the same time, it is necessary to detect and inspect the high pressure post insulators regularly in order to avoid fracture. In cold areas, it is best to apply polysulfide waterproof glue to the cement casting parts of their electrical equipment.
5、Conclusion
To sum up, the insulation technology of high voltage electrical equipment can detect and monitor the insulation state of the equipment in time, which plays an important role in the insulation failure of the equipment and ensuring the stable and safe operation of the power grid. Insulation technology is the basis and the only technical means to implement state maintenance in power system. It is necessary to promote the use of insulation technology, accumulate experience and carry out state maintenance of high voltage electrical equipment. Nowadays, the continuous development of computers, communications and sensors provides a guarantee for the development of insulation technology for high voltage electrical equipment. It provides a strong support for the research and development of ultra high voltage power line insulators and insulation technology. (author: Tian Hui Zi, Zhao Yao, Jia Guangliang)